Coil winding machine



Feb. 9, 1954 DE wl'r'r T. vAN ALEN 2,668,670

COIL WINDING MACHINE Filed Dec. 15, 1947 2 Sheets-Sheet l mffilllllIIIIIIIIIIIIIIIIIIIIIIHMZ N l INVENTOR Ik DeWitt T. Vcm Alen BY m,

ATTORNEY DE WITT T. VAN ALEN Feb. 9, 1954 COIL WINDING MACHINE 2 Sheets-Sheet 2 Filed Deo. 15, 1947 mvr-:NToR DeW t'r T. Von1 Alen ATTORNEY Patented Feb. 9, 1954 COIL WINDING MACHINE De Witt T. Van Alen, Delavan, Wis., assgnor to The George W. Borg Corporation, Delavan, Wis., a corporation of Delaware Application December 15, 1947, Serial No. 7 91,820

8 Claims.

The present invention relates in general to coil winding machines and more in particular to winding machines which are adapted to wind single layer coils of resistance wire on strips of insulating material in the manufacture of re sistance elements for rheostats and potentiometers.

The invention is applied to a coil winding machine oi the type disclosed in the application of Gilman et a1., S. N. 563,522, filed November 15, 1944, now Patent 2,466,227. In making a resistance element on this machine the strip is rotated to wind the resistance wire thereon and is moved longitudinally to space the successive turns apart. The longitudinal movement of the strip is gov erned by a cam having a rise equal to the length of the winding space and connected by reduction gearing to the spindle which rotates the strip. Thus the number of turns of wire in a given length winding space can be accurately predetermined in accordance with the desired total resistance of the winding.

The calculation of the number of turns in volves an assumption as to the resistance of the wire per unit length. The resistance is known or can be measured accurately but it is impracticable to measure the resistance of the Wire for each resistance element. The value of the resistance is therefore taken as the average value obtained by measuring a number of samples. Due to slight variations in wire size, composition of the alloy, and other factors, it is found that resistance elements having the same number of turns and wound on strips of the .same width and thickness (so far as can be made) will vary considerably in total resistance.

It is the object of the invention to overcome the foregoing dilculty and make possible the quantity production of resistance elements hav ing the same total resistance notwithstanding variations in the resistance oi the wire. The desired result is accomplished by automatically and continuously testing the resistance oi` the winding as it is formed and increasing the turn spac ing if the resistance starts to increase too fast and decreasing the turn spacing ii the resistance ci the winding increases too slowly. Thus if the resistance of the wire 'is higher than the assumed value less turns are put on the strip While if the resistance of the wire is less than the assumed value more turns are put on.

A feature of the invention is a diiierential mechanism which ei'ectively changes the gear ratio between the spacing cam and the spindle which rotates the strip. The di'ierenti'al mecha- 2 nism is controlled by the resistance testing means and increases or decreases the gear ratio as required` The invention will be described more in detail in the ensuing specication, reference being had to the accompanying drawings, in which- Fig. 1 is a diagrammatic representation of a coil winding machine modied in accordance with the invention;

Fig. 2 is a cross section through the differential mechanism; and

Fig. 3 is a diagrammatic circuit drawing showing the electrical equipment and connections thereof.

The coil winding machine shown in Fig. 1 includes a so-called head stock I0 and tail stock I I which are connected by the rod I2 and are slidable in ways like the corresponding parts in a lathe. The sliding movement of the head stock and tail stock is brought about by means of compressed air. The cylinder I3 has a piston which is connected to the head stock I by the piston rod I 4. Compressed air from the supply pipe I6 may be admitted to either end of the cylinder I3 by means of the valve I5, whereby the head stock and tail stock may be moved to the right or left as desired. These parts are shown in their extreme right hand position in the drawing. The limit of movement in this direction may be determined by a suitable stop or by the piston engaging the closed end oi the cylinder. Movement of the head stock and tail stock to the left is controlled by the cam Il, having the cam follower I8 which is connected to the tail stock II by the rod I9.

The strip of insulating material 2li, on which the wire 25 is to be wound to make a resistance element, is supported on the spindles 2l and 22 by means of suitable collets, details of which are not shown. The spindles are rotatably mounted on the head stock Ii] and tail stock I I, respectively, and are adapted to be rotated by the spur gears 23 and 2li which mesh with the wide faced pinion 2B. This pinion is mounted on the shaft 21 which is driven by the motor 28 by means of the belt and pulleys shown.

The lshaft 2l also drives the cam il which with the gear 37 is mounted on the shaft 3.8. The driving connection between shaft 2l and shaft 38 comp-rises the gears 3|, t2, 32', and 33, the latter of which is mounted on the shaft 39, the diierential mechanism in housing 35, shaft 36, worm lill, and gear 31. The cam Ii rotates very slowly as compared to the spindles 2i and 22 and it will be understood therefore that the speed reduction in the gear train is considerable. There may be a 100 to 1 reduction in the worm 40 geai` 31 connection and a 3 to 1 reduction in the dilerential. The gearsV 3I, 32, 32' and 33 are members of a set of interchangeable gears by means of which the speed ratio can be varied within wide limits.

The differential mechanism is shown in vdetail in Fig. 2. The input shaft is shaft 39 on which gear 33 is mounted. The output shaft is shaft 35 which carries the worm 40. The housing V35 has a central hub 4I by means of which it is rotatably mounted on the shaft 39. Inside the housing 35 there is a spur gear 42 fixed on shaft 39 and a spider 43 xedly mounted on shaft 36. Supported on the spider 43 are a plurality of pin. ions such as 44 and 45 which mesh with gear 42 and also with the internally toothed gear 45 which is fixed to the inner wall of the housing.

The housing 35 is normally stationary but may be rotated in either direction by means of gear 34, worm 48, and the reversible motor 41. When the housing 35 and gears 34 and 46 are stationary shaft 39 drives shaft 36 at 1/3 its own speed, that is, there is a 3 to 1 speed reduction as previously mentioned, When the gear 34, housing 35 and gear 4t are rotated in the same direction as the direction of rotation of shafts 39 and 36 the speed of the latter shaft relative to shaft 39 is increased, but when the gear 34,

housing 35, and gear 45 are rotated in the opposite direction the speed of shaft 35 is decreased.

The reference character indicates a switch which is actuated by an adjustable stud 5I carried on the front end of the tail stock I! when z3.;

the latter reaches the end of its movement to the left. It is the closure of this switch which stops the movement as will be explained subsequently.

The spindle 22 has an insulated sleeve or slip ring 52 near the end, which is engaged by the brush or wiper 53. The latter is mounted on the tail stock I I by a suitable insulating bracket such as 54. The wire 25 is secured to the slip ring 52 in any suitable manner, by means of the small screw 55, for example. After passing around the strip 20 the wire passes around the pulley 56 and thence by way of the tensioning mechanism to the supply spool on which it is wound. The pulley 55 is made of conducting material and is mounted on a fixed part of the machine by the support 57. The pulley 56 thus affords means for grounding the wire substantially at the last turn on the strip. In practice it is grounded Very nearly at the strip since there is an intervening guide wheel or pulley which guides the wire directly on to the strip, as shown in the Gilman et al. application previously referred to.

The reference character 60 indicates a rack which is slidably mounted like the head stock and tail stock. The rack is moved to the left by the member 6I mounted on the head stock I0 and adapted to engage the adjusting screw 52 mounted on the rack when the head stock moves to the left under control of the cam I 1. This movement of the rack tensions the spring 61 which returns the rack to its right hand position, after the head stock has returned, under control of the dash pot 65. The dash pot contains a piston which is connected to the rack 60 by the piston rod 55 and has a valve 68 near the end for regulating the admission and ejection of air. The limit of the raeks movement to the right is determined by engagement of the adjusting screw 64 with the stop 63.

The reference character l0 indicates a potentiometer, which is preferably of the type disclosed in the pending application of Gibbs et al., S. N. 573,680, led January 20, 1945. This potentiometer has a resistance element in the form of a ten turn compound helix connected between terminals i3 and 'I4 and a rotatable brush driven by the shaft 'li and connected through a slip ring arrangement to the terminal l5. The shaft 'Il is rotated about 9 or 91/2 turns by the pinion l2 and rack 50 during the movement of the rack to the left., When the parts are in the position in which they are shown in the drawing the rotatable brush is in engagement with the resista-nce element at terminal 'i3 and the resistance between terminal l'3 and terminal 'l5 is zero, or substantially zero. As the shaft 'II rotates, the brush travels along the resistance element and the resistance between terminals T3 and l5 increases,

approaching the maximum resistance after 9 or 9% turns. Terminal 74 is not used.

The potentiometer I0 should be carefully s elected so as to aiford the best possible resistance curve, which should be linear or as near an approximation as can be made. The effect of such unavoidable departures from linearity as may be present are minimized by the great length of the resistance element, about 42 inches, requiring an angular movement of the brush of around 3240 degrees or more.

The potentiometer 8l! is similar to potentiometer 70, but need not be so accurate as regards linearity of its resistance curve. The terminals of the resistance element are indicated at 'I6 and il, while 73 is the terminal connected to the movable brush.

Referring now to Fig. 3, the motors 41 and 28 of Fig. 1 are shown and are indicated by the same reference numerals. Also the switch 50 and the actuating stud 5I on the tail stock. y

The potentiometer l0 is included as one arm of the bridge circuit 00. The other arms are the resistance I3 I, the variable resistance or rheostat IIJZ, and the resistance wire 25 of the resistance element which is wound on the machine. The potentiometer l! may have a total resistance of about 10,000 ohms, resistance IOI may be 20,000 ohms, and the rheostat I02 may have a range up to 20,000 ohms. These values are suitable for winding resistance elements ranging from sev.- eral thousand ohms up to about 10,000 ohms.

Current is supplied to the bridge circuit from the potentiometer 30 which is shunted across the secondary winding of the transformer I 06. It is thought that the circuit connections of the bridge will be clear without detailed explanation. It may be pointed out, however, that the junction point 53 is the brush 53 of Fig. 1 which is conductively connected with the end of wire 25 during the winding of the resistance element. The slider 56 is the pulley 56 of Fig. 7, which is in conductive connection with the Wire where it leaves the strip. Y

The control circuit including the tubes I I0, I I I, and I I 2 may now be described briefly.

The junction point It? on the bridge circuit |00 is connected by a conductor 03 to the grid of the tube H0, which may be a type 6F15 tube and operates as an amplifier.

The plate circuit of tube I I0 is connected by way of the condenser I I3 and the resistance H4 to the grid of tube III, which may be another type 6F15 tube. The tube II I has a positive bias and functions as a positive half cycle eliminator.

A positive plate voltage is supplied to the tubes and over conductor. H from the'rcctier comprising the transformer H5 and the full wave rectifier tube I6. This rectifier also .supplies4 the positive biasing voltage to the grid -of tube ||1 as will `be explained briefly,

The biasing connection .includes the potentiometer |20, having the slider |2|, the resist,- ance H8, and the resistance H9. The amount of positive bias is determined by the position of the slider |2| and should .be suhicient to cause the grid to draw current. The amount of grid our rent which can flow is limited by the resistance H4. This resistance is preferably at least one.

halfv megohm, and is high relative to the internal resistance between the cathode and grid in the tube, so that the major portion of the biasing voltage appears across the resistance 4 and only a small fraction of it between the grid and cathode. The effect is to give the tube a plate current curve which levels oli sharply at the point where the grid becomes positive .and .starts to draw current. Positive half waves ol signal voltages transmitted from the preceding stage via condenser H3 accordingly have very little effect von the plate current at tube IH. negative half waves of such signal voltages, .how

`ever, if strong enough to overcome the positive grid bias, cause large .fluctuations in the plate current. The potentiometer is used to control the sensitivity of the circuit. .Decreasing the i f lpositive bias increases the sensitivity, that is,

it lmakes .the tube responsive to negative vsigna-l .voltages of Asmaller amplitude, while increasing the positive bias decreases the sensitivity.

The plate circuit of tube lil is coupled by means of the condenser |22 to the grids of the tube |2 which may be a type SSN? double triode. The grids of tube i2 have a negative bias, derived by way of resistance from the biasing circuit which includes the potentiometer |23 and resistance |25, and the tube responds to positive impulses which are generated at tube in response to negative signal impulses. The value of the negative bias is adjusted by means of slider |24 and should be sucient to cause the tube toioperate on an eicient part lof its plate current curve.

The plate circuits yof the tube ||2 are supplied with current by the center tapped secondary winding of the transformer |34. One plate circuit includes the cathode of the tube, the plate |30, relay |32, and the upper half of the secondary winding, and carries current .at times when the junction point |35 is positive, provided there is a positive potential on the grid. The other plate circuit includes the cathode of the tube, the plate |3| relay |33, and the lower half of the secondary Winding, and carries current at times when the junction pointV |31 is positive, if there is a positive potential on the grid. When junction |36 is positive, junction |31 is negative and vice versa, that is, the effective plate voltages applied to the plate i3!) and |3| are 180 degrees out of phase with each other. of the tube ||2 receive only one positive impulse per cycle and these impulses are in phase with the positive potentials applied to the plate i3d or with the positive potentials applied to the plate |3|, depending on the direction in which the bridge |00 is unbalanced, but cannot be in phase with both. Thus only one of the two relays v|32 and |33 can energize. under any given condition of unbalance.v

It'will be understood that the "in phase rela-- The When the circuit is functioning, the grids tion-between the positivepotentials applied to the plate |30 or plate 13| of tube 1.12A and the positive impulses received .at the grids -ofl the tube in response to an unbalanced 1conditirm.' at the bridge 10|! results from the `fact that the transformers |06 .and |34 are supplied with power from the lsame source of alternating `current.

The relays |52 and .|33 control the electroe magnetic switches |141) and |41, respectively, which operate the motor 41.

The resistance |42, shunted by condenser |43, is common to both plate circuits of the tube H2 and provides a feed back voltage, as will be explained more fully later on.

The potentiometer |48, having adjustable slider i349, provides a positive potential, known as throttling voltage, which is applied to the grid oi tube whenever relay |32 4or |33 energizes. The contacts |46 and 41, shown detached for convenience, are on the relays |32 and |33, respectvely. The function of the throttling voltage will also be explained later on.

JThe bracket |04 indicates a source of three phase alternating current which supplies power for operating the motor 41 under control of the manually operable switch S2 and the electromagnetic switches |Ll0 Aand Ml.

The bracket |05 indicates a source of `single phase alternating current which supplies power to other parts of the apparatus. A switch 'Sl connects the said source to the transformer H5, transformer 13d, and to the circuits for the electromagnetic switches and |41. Another switch S3 connects the source |65 tothe motor 28 and to the transformer |06.

The operation of the machine may now be described. It may be assumed for this purpose that it is desired to wind resistance elements having a resistance of 5,000 ohms. Any other resistance within reasonable limits could be selected but this will serve as an example and aford an opportunity of explaining the procedure.

The length of the winding space on the strip auch as 20 is known, also the width and thickness of the strips, which gives the length of each turn. With this information and standard wire tables, it is possible to determine the size of wire to be used and the number of turns which will be re quired in order to give a total resistance of 5,000 ohms. The number of turns required for the desired total resistance depends on the wire size, and the latter should be so selected that the corresponding number of turns will go into the winding space with a medium spacing which can be vincreased or decreased if necessary to correct for variations in wire resistance.

The number of turns having been determined, the gear ratio between the spindles 2| and 22 and the cam il' can be calculated and the proper gears such as 3|, 32, 32', and 33 can be installed. The gear ratio should be such that during the angular motion of the carri in winding a strip, about 340 degrees, the spindles make a number of rotations equal to the number of turns.

The cam |1 is a straight line cam and should have a rise equal to the length of the winding space.

With the apparatus in the position in which it is shown in Fig. l, the adjusting screw 84 should adjusted to set the potentiometer 10 to zero,

that is. with the movable brush 15 at the terminal `13 end of the resistance element, as shown in Fig. 3. This willalso adjust potentiometer 8D to zero, but if it does not, the necessary adjustment is accomplished by rotating the potentiometer while the pinion is in engagement with the rack.

Compressed air may now be admitted to the right hand end of cylinder I3 by means of valve I5, thereby moving the headstock assembly and strip 26 to the left and causing the follower I8 to engage the cam In this position of the parts the member 6| should engage the end of adjusting screw 62 without, however, bringing about any movement of the rack 60. The screw 62 should be adjusted, if necessary, to fuliill these conditions. The switch S3, Fig. 3, may now be closed to start the motor 28. The wire 25 has not yet been attached to the slip ring 52. Motor 28 rotates the spindles 2| and 22 and the cam |'l and is allowed to run until the cam has rotated the amount it is required to rotate in winding a strip, assumed to be 340 degrees. The motor is then stopped by opening the switch S3. The headstock assembly is now in its extreme left hand position and the stud 5| is adjusted so that it will operate the switch 50 at this point. This provides for automatically opening the switch S3 by means of solenoid |52 during actual Winding operations.

The movement of the headstock assembly to the left causes a corresponding movement of the rack 60, whereby the shaft 1| of the potentiometer I is rotated about 9 or 91/2 turns. The

amount of rotation is not vcritical but should be sufcient to utilize the major portion of the resistance element. The movable brush 15 of the potentiometer will therefore be near the terminal 'I4 end of the resistance element. The shaft vof potentiometer 80 is rotated at the same time as shaft 1| and accordingly the movable brush 18 will be near the terminal end of the resistance element.

The next operation is to adjust the bridge |00 for winding 5,000 ohm resistance elements. This connecting an A. C. voltmeter between the grounded terminal 15 and the junction |01 on the bridge. When the bridge is balanced there will be no diierence of potential between these points. The adjustment of rheostat |02 having been completed the rheostat is left in adjusted position and the known 5,000 ohm resistance is removed from the strip arm of the bridge.

rihe operator may now shift the valve so as to admit compressed air to the left hand end of cylinder I3, which incidentally opens the other end to the atmosphere. The headstock assembly is thus moved rapidly to its extreme right hand position, the position in which it is shown in Fig. l. The rack 60 is moved to the right also under the influence of spring 61 but at a slower speed because of the dash pot 65. The potentiometers and 80 are thus reset to zero resistance.

The switch S3 may now be closed for a long enough interval to advance the cam |1 to its starting position. This is the position in which the cam is shown in Fig. 1. The valve I5 is then reversed so as to admit air to the vright hand end ofcylinder B and place the headstock assembly under'the control of the cam I1.

The machine is now ready to proceed with winding operations and the switches SI and S2 can be closed so as to supply current to the control circuits.

It has been assumed that the strip has previously been placed in the machine. The wire is carried on a supply spool the rotation of which for delivering wire to the strip during winding thereof is controlled by tensioning apparatus. This apparatus is not shown herein since it is no part of the invention but is shown and described in the previously referred to application of Gilman et al. It will suffice to say here that the operator proceeds by taking the end of the wire from the spool and threading it through the tensioning apparatus, after which the wire is passed around the pulley 56 and the strip 20 and the end is secured to the slip ring 52 by the screw 55.

The operator may now close the switch S3 to again complete the circuit of motor 28. The motor rotates the spindles 2| and 22 and the strip 20 supported thereon, and accordingly the wire 25 is wound on the strip in spaced turns, the cam |1 being rotated slowly at the same time in order to space successive turns apart. The spacing at the start is in accordance with the calculated number of turns required to give the desired resistance of 5,000 ohms.

As the winding operation proceeds, the shafts of the potentiometers 10 and 80 are rotated by the rack 60. The brush 18 of potentiometer 80 is therefore moved away from terminal 16 and toward terminal to gradually increase the voltage applied to the bridge circuit |00, and thereby maintain lits sensitivity substantially constant. 'I'he brush 15 of potentiometer 'l0 is moved away from terminal 13 and toward terminal 14 and the resistance of the potentiometer arm of the bridge, which is zero at the start, is gradually increased. At the same time the pully 56 maintains a ground connection to the wire 25 where it leaves the strip 20 and accordingly the resistance of the strip arm of the bridge, also zero at the start, is gradually increased. If the increase in the resistance of the strip arm is in accordance with the previous calculations it will be proportionate to the increase in the resistance of the potentiometer arm and the bridge |00 will remain in balance.

It may be assumed now that the wire 25 is somewhat oversize and therefore has less re-' sistance per turn than it should have. In accordance with this assumption, the resistance of the strip arm will increase too slowly in proportion to the increase in the resistance of the potentiometer arm and the bridge will become unbalanced.

The unbalanced condition of the bridge results in an alternating potential between ground and the junction |07 on the bridge and an alternating current flow is established which produces a drop across the resistance |53. The alternating voltages thus developed are applied to the grid cathode circuit of tube ||0 where they are amplified in the usual manner.

The output of tube ||0 is alternating in character and is transmitted to the grid circuit of the control tube by way of condenser H3. Due to the positive bias on the grid of this tube the positive half waves of signal current have no effect, as previously explained, but the negative half waves produce drops in the plate current through the tube as soon as they become strong enough to overcome the small positive bias. The .resulting positive impulses'produced at the plate of the 9 tube are'transmitted by way of the condenser f22 to the grids of tube I I2.

The positive impulses received at the grids of tube H2 are in phase' with the positive potentials which are applied to plate |30 of the tube by the transformer |3c and are 180 degrees out of phase' with the positive potentialsv applied to plate |35. Hence no current can iiow in the circuit of plate 3| and relay |33. Relay |32 is energized, however; over a circuit which may be traced from the center tap of winding 35, by way oi' conductor it", resistance |42, ground, cathode 01"' tube H2, plate |30, relay |32, and the upper half of winding i315 backv to the center tap oi" the winding. Current flow in this circuit develops a pulsating negative D. C. voltage on conductor ld, due to the drop across resistance |152, which is fed back by way' oi' resistance Illll to the gridl of tube i I, thereby reinforcing the negative half waves of the signal voltage. These feed back impulses insure positive energizaton oi relay |32. The condenser bridged around the relay is charged each timeA current flows in the relay circuit, that is, during each half cycle` when junction |33 is positive, and discharges through the relay during the intervening half cycles, thereby maintaining the relay ener'- gized in spite of the intermittent current i'loW' in the rest of the circuit'.

Upon energizing, relay |32/ opens a point in the circuit of electromagnetic switch titi at contact |55, and at contact |55 closes the circuit of electromagnetic switch |46', which energizesv and at contacts itl and |56 completes circuits from the three phase power supply source itt' to the motor 4'1. 'Ihe motor lll now starts up and rotates the gear 34 of the differential mechanism in the proper direction to decrease the speed of shaft 36 and the speed of cam il' driven thereby; The eiect of this is to decrease the turn spacing, or increase the ratio of turns to unit movement of the cam, which amounts to the same thing. Thus the operation of motor il begins to correct' for the low resistance of the wire 25.

Returning now to relay |32, when this relay energizes, it closes its contact' lie and thus applies a positive throttling voltage from the p'otentiometer M8 to the grid circuit oi tube by way of conductor |69, which connects to the grid circuit at junction ll. The positive throttling voltage is high enough tocancel the' negative feed back impulses transmittedv over the conductor |52 in the feedback circuit and maintain the positive bias on the grid of tube lil at a value which is somewhat higher or more positive than the bias derived from the sensitivity control potentiometer |20. This gives the relay T32 a chance to lde-'energize as soon as the correction initiated by starting motor il has proceeded far enough to substantially reduce the strength of the out'- put impulses from the control tube. This action takes place very fast and the relay may restore almost immediately.

. The restoration of relay |32 stops the motor .dT and opens contact Hit, thereby cutting off the throttling voltage from the grid circuit oi tube The high positive bias on the grid does not return to its normal low value at once, however, due to the fact thatY condenser |45 has become charged and maintains the grid bias higher than normal for a. period of a few cycles as it discharges through the resistance |44`.

As the positive-bias returns to its: normal value the, sensitivity of. the. tube Iii increasesA and ii the bridge is still unbalanced the: negative half Waves of signal voltage will again produce drops 1G in plate current, whereby positive impulses arel again transmitted to the grids of tube |12 to op erate relay |32 and start the motor lil'. Thepreviously described operations are thus repeated. The operation from here on depends on the re-l si'stance of the wire being wound on the strip. If the resistance of the remainder oi the wire is normal a few correcting operations will bring the bridge in balance. Ii: the Wire is uniformly of too low resistance throughout its length, how-r over, the bridge will continually become unbali anced and the correcting operations willA berepeated' throughout' the' winding of the strip.

when the winding is completed, the stud 5T closes switch eil', thereby energizing solenoid |52 to open switch and stop the machine. The wire is now cut off and the ends of the winding may be secured in place by tape', pending the ap*-V piication of permanent terminals. Screw 55 is then loosened, the wire is disconnected from the slip` ring: 52 and the wound strip is' removed from the machine. Another strip` may now be in-V serted and wound' in the sainev way asv described. In the course or further winding operations a spool of wire may' be encountered which has too" high a' resistance. When a strip' is wound" with this high resistance wire the bridge; will become` unbalanced shortly after the' winding starts but in this case it' will become unbalanced' in the 0p"- posite direction and the output current from the bridge will be degrees out oi phase with the" outputcurrent which resulted from the former condition of unb'alance. The positive impulses transmitted from the control tubev |`I I' to` thegrids of tube H2 will therefore be in phase with the positive potentials applied to plate |'3I' and relay |33 will be energized. Relay' |33 operates the electro-magnetic switch 4| which closes circuits for motor e? as shown, which now reverses its former direction of rotation and: rotates the gear Se of the differential mechanism in the proper direction to increase the speed of shaft 35 and cam li'. Thus the turn spacing is irrcreased' and the' number' of turns is decreased to' compensate for' the higher resistance of the wire. The correcting operations'. are otherwise the same as described' and need not be gone overagain;

In case a question shouldl arise as' to" why a; condition of unbalance resulting from too low wire resistance operates relay |32 rather than relay |33", orwhy' the opposite condition of um' balance operates relayl #33 rather than relay |32, it may be stated that the properv phase relationship depends on the' primary windings of the transformers Eile and |34 being correctly con-V nected to; the line; `When the machine is rst set up and tested, if it is found that' themotor lll runs in the wrong direction inlresponse to an unbalanced condition of thebridge, the trouble may bei corrected by reversing the connections t'o one of the-primary windings.

While the invention has=been described incont-v nection with the winding of` a linear resistance element', it should be' pointed out that it is' also' appl'icable'to thewinding of non-linearresistance elements'. It' is welll adapted', for example, to the winding. ofr non-linear resistance elernent'sp suc-li as disclosed in my pending application Serial No. 602313 filed July 2`, 1945', in which` uniform d'- ameter Wire. is used. and a variable spacingis` employedv tol give the desired` non-linear. characteristicto the resistance curve. Tapered.y wire may also be usedi to give ther desired. resistance curve,

- either alone or in combination with a variable have a resistance curve which is the same as the resistance curve of the resistance element to be wound.

The invention having been described that which is believed to be new and for which the protection of Letters Patent is desired will be pointed out in the appended claims.

I claim:

1. In a coil winding machine, means for rotating a strip of insulating material to wind a resistance wire thereon, means for moving said strip longitudinally to space the turns of the winding a predetermined distance apart, means for comparing the rate at which the resistance of the winding increases during the Winding operation with a standard rate, means controlled by said comparing means for automatically changing the spacing if the rate at which the resistance of the winding increases is too fast or too slow said means for changing the spacing including gearing between the respective means for rotating and for moving the strip, and said gearing including a differential mechanism provided with separate motor means connected to and controlled by said comparing means.

2. In a coil winding machine, means for rotating a support to wind a resistance wire thereon, means geared to said rotating means for moving said support longitudinally at a predetermined rate to space the turns of the winding, means for testing the resistance of the winding as the winding operation proceeds, and means controlled by said testing means for automatically changing the gear ratio between said rotating means and said moving means if the resistance of said winding becomes too high or too low, said means controlled by the testing means including for the gear connections a diierential provided with separate motor means responsive to said testing means.

3. In a coil winding machine, means mounted for progressive movement for winding a wire on a support to form a resistance element, means including a bridge circuit for testing the resistance .of said winding as the winding operation proceeds,

said bridge circuit having two bridge arms ofv which one arm is said winding and the other arm is a resistance which increases during the winding operation, means for supplying operating current to said bridge circuit, and means connected with the means for winding the wire automatically in response to the progressivev movement to increase the voltage of said current in proportion to the increase in the resistance of said arms.

4. In a coil winding machine, means including an electrically controlled motor for correcting the rate for Winding a wire on a support to form a resistance element, means including a bridge circuit for testing the resistance of said element as the Winding thereof proceeds, said bridge circuit having two bridge arms of which vone is the said element and the other is a rheostat having a movable contact, means for supplying operating current to said bridge, said last means including a current regulating device having a movable con- Y tact, and means operative during the winding of said element to rotate the movable contact of said rheostat in the proper direction to increase itsY effective resistance and to simultaneously rotate the movable contact of said regulating device in the proper direction to compensate for the increasing resistance of said arms, the regulated current being connected for the control of said motor;

5. In a coil winding machine, means for sup` porting a strip of insulating material, said means including a rotatable and endwise movable spindle, a source of power for rotating said spindle to thereby rotate said strip and wind a resistance wire thereon, means including a device geared toV said spindle, a bridge circuit in which said wind-v ing and said rheostat form two opposite arms, a differential mechanism having a reversible motorv for the control of the output thereof and included in the gearing between said device and vsaid spindle, and means responsive to an unbalanced condition of said bridge circuit and dependent on the direction in which the bridge circuit is unbalanced to .operate the motor of said differential mechanism to increase or decrease the rate of longitudinal movement of said strip relative to its rate of rotation.

6. In a coil winding machine, means for holding and rotating a strip adapted to form a support for a coil, means for feeding Wire to said strip at a iixed point to form a coil on said strip responsive to its rotation, means for progressively' advancing said holding and rotating means to move said strip past said xed point to space the turns of the coil, a connection between said rotating means and said advancing means including suitable gears and a differential mechanism having a separate motor for the control of the output thereof, a rheostat having a rotatable contact, means responsive to operation of said advancing means to rotate said contact, a bridge circuit in' proportionate to the increase in the resistance of said rheostat.

i 7. In a coil winding machine, means for Winding a resistance wire on a support, including means'for feeding the wire to the support, 'ad'- vancing means for producing relative movement between said support and feeding means to space the turns of the winding, means for continuously testing the resistance of the winding as the winding operation proceeds, said last means including a bridge circuit in which said winding and a cor-Y respondingly varying portion of a standard resistance form two opposite bridge arms, respectively, a source of alternating current included in said circuit and operative to produce an'alternating output voltage when theV bridge is unbalanced, means for amplifying said voltage and for eliminating alternate half Waves to produce a signal comprising successive positive pulses which are in phase with the positive or negative half waves from said source depending on whether the resistance of the winding is too high or too vlow relative to the standard resistance, two space discharge devices having grids to which said signal is applied simultaneously, plate circuits for said devices supplied with operating voltages responsive to the positive and negative half waves from said source, respectively, two relays in said plate circuits, respectively, one or the other of which is energized depending on the phase of the signal pulses, and means responsive to the energization of either of said relays to change the speed of said advancing means relative to that of said winding means, the energization of one relay being effective to increase the speed while the energization of the other relay is eective to decrease the speed.

8. In a coil winding machine, means for winding a resistance wire on a support, including means for feeding the wire to the support, advancing means for producing relative movement between said support and feeding means to space the turns of the winding, means for continuously testing the resistance of the winding as the winding operation proceeds, said last means including a bridge circuit in which said Winding and a correspondingly varying portion of a standard resistance form two opposite bridge arms, respectively, means comprising suitable gears and a differential mechanism connecting said winding means and said advancing means, a reversible motor for operating said differential mechanism to speed up or slow down said ad- Vancing means relative to said Winding means, depending on the direction of operation, a circuit or running said motor in each direction, two relays for closing said circuits, respectively, two space discharge devices having anode circuits including said relays, respectively, and sources of alternating anode voltage 180 degrees apart in phase, and means including said bridge circuit operating to transmit positive pulses to the grids of said devices which are in phase with the anode voltage at one device in case the resistance of the winding increases too slowly and in phase with the anode voltage at the other device in case it increases too fast. DE WITT T. VAN ALEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,500,605 De Lange et al. Mar. 14, 1950 FOREIGN PATENTS Y Number Country Date 120,713 Australia Dec. 24, 1945 

